Anammox in a UASB reactor treating saline wastewater

The feasibility of an anammox (anaerobic ammonium oxidation) UASB (upflow anaerobic sludge blanket) bioreactor to treat ammonium-rich brines was investigated in batch and continuous-flow experiments. The evidence from batch tests indicated that the anammox activity was significantly inhibited under highly saline conditions while the inhibition was reversible. Saline shock loading of 30 g NaCl l−1 caused a 67.5% decrease in specific anammox activity (SAA) compared to reference biomass (not exposed to salt). However, the acclimatized biomass displayed a SAA value just 45.1% lower than that of the reference biomass. When transferred from brine to freshwater, the salt-exposed biomass resumed its activity by 43.1%. Subsequent to appropriate acclimatization, careful manipulation nitrite concentration, nitrogen loading rate (NLR), and other operational parameters for 77 days, the results of continuous-flow experiment revealed that under the salinity of 30 g NaCl l−1 the reactor performed well and the substrate removal capacity (nitrogen removal rate, NRR, of 448 ± 15 mgl−1 d−1) was comparable to the condition of freshwater (NRR of 464 ± 13 mgl−1 d−1). However, the anammox UASB bioreactor was prone to malfunction under transient operating conditions.

► The feasibility of an anammox UASB bioreactor to treat ammonium-rich brines was investigated.
► The anammox activity was significantly inhibited by saline shock loading while the inhibition was reversible.
► Subsequent to appropriate acclimatization, the reactor performed well under the salinity of 30 g NaCl l−1.